1. Field of the Invention
The present disclosure relates to a float bath for manufacturing a float glass and a cooling method of the same. More particularly, the present disclosure relates to a float bath for manufacturing a float glass, having an improved structure for cooling a bottom casing surrounding bricks storing a molten metal, and a cooling method of the same.
2. Description of the Related Art
Generally, an apparatus for manufacturing a float glass (also known as sheet glass, flat glass, or plate glass) using a float glass process is used to manufacture a band-shaped (or, ribbon-shaped) float glass having predetermined width and thickness by continuously supplying molten glass onto a flowing molten metal stored in a float bath, floating the molten glass on the molten metal to form a molten glass ribbon, and pulling up the glass ribbon toward an annealing lehr near an exit of the float bath.
Here, the molten metal includes, for example, molten tin or molten tin alloy and has a greater specific gravity than the molten glass. The molten metal is received in a float chamber where reducing hydrogen (H2) and/or nitrogen (N2) gas is filled. The float chamber includes a bottom storing molten metal and a roof covering the bottom. In addition, the bottom (or, the float bath) storing molten metal has a horizontally extending structure and includes a high heat resistant material therein. The molten glass is supplied from an upstream side of the float bath onto the surface of the molten metal and forms a molten glass ribbon while moving to a downstream side. The molten glass ribbon is lifted up at a location (hereinafter, referred to as a take-off point) set on the downstream side of the float bath to be kept away from the molten metal, and is delivered to an annealing lehr of the next process.
Meanwhile, the molten metal in the float chamber is maintained at a high temperature (about 600° C. to 1,100° C.) and has a melting point of 232° C. Therefore, the bottom portion of the float bath needs to cool to a predetermined temperature. Otherwise, the molten metal may react with a base casing made of carbon steel material to create holes in the base casing, which may allow the molten metal to leak out of the float bath. In addition, in aspect of quality, if the inner temperature of the float bath changes (for example, −5° C. to +5° C.), the flow of the molten metal changes to generate bubbles, which may cause surface defects (for example, OBB (Open Bottom Bubble) or BOS (Bottom Open Seed) to a final product of the float glass. Therefore, the final product of the float glass produced through the float bath should maintain uniform temperature distribution in the float bath in aspect of quality, particularly OBB.
However, a general float bath system cools the bottom of the float bath by blowing a cooling air to the bottom casing by using an air blower. The cooling device using such an air blower uses a plurality of nozzles. Here, each nozzle has a diameter of about 60 mm, and a pitch between the nozzles is about 500 mm. In addition, an interval between the end of the nozzle and the bottom casing is about 300 mm. When measuring the temperature of the bottom of the above float bath system, the bottom has a highest temperature of 146.8° C., a lowest temperature of 69.1° C., and an average temperature of 103.5° C. Due to the large diameter of the nozzles used in the air blower for cooling the bottom of the float bath and the large pitch between the nozzles along with the large interval between the nozzle and the bottom casing, it is not easy to uniformly maintain the inner temperature of the float bath.